From Seeking Alpha
In recessions, cash is short and businesses and individuals seek to raise cash by any means practical in order to prepare themselves for the tough times ahead. In a world in which U.S. currency is held as the global reserve, cash means U.S. dollars. In short, institutions and individuals are selling any asset that is not nailed down (stocks, corporate bonds, etc.) and buying U.S. dollars. This has resulted in plummeting asset prices and a rising dollar. However, this dynamic cannot exist in perpetuity.